Sterling-based conference call company Speek has added a fresh round of capital to its coffers, executives said Monday.

The 2-year-old firm has raised $5.1 million, including $2.7 million in previously announced convertible notes. The money will allow Speek to bulk up its sales staff as it starts selling software to companies, said chief executive John Bracken.

Speek aims to alter the way businesses conduct the standard conference call by moving it online, giving participants the ability to more easily keep track of who is on the call and speaking at any given time.

The company started with a free version of the software for average consumers, then added a professional version for those seeking a more sophisticated experience. Now, they’ve begun selling directly to companies for $10 per user per month.

“Most of the money is going to build our sales team around the Speek for Teams product,” said co-founder and chief technology officer Danny Boice. “That’s our top revenue generator so we’re really focused on selling that product and building a sales team around it.”

The latest round includes several repeat investors. The participants include 500 Start-ups, Paul Singh’s Crystal Tech Fund, Middleland Capital and CNF Investments, the Clark Enterprises venture fund, among others.

Speek counts 16 employees to date, Bracken said.